The present invention relates to a needling machine used for the mechanical consolidation of a sheet -or fleece- of fibres coming, for example, from a spreading and fleecing machine (so-called "cross-lapper").
Known needling machines comprise a support called a board on which needles are fixed. By means of crank and connecting rod devices, the board is moved in an alternating -i.e. reciprocating- manner in order that these needles traverse the sheet of fibres at a production rate which can range from 1000 to 2000 strikes per minute.
Complementary devices also make it possible to regulate the flow of fibres entering and leaving the machine, with or without stretch, and at speeds chosen according to the strike rate expressed as a number of strikes per minute, which is equivalent to the number of alternating movements of the needles per minute.
Conventionally, the connecting rod of each crank and connecting rod device extends between an eccentric, connected to a motor, and an articulation at the end of a sliding rod to which is fixed a needle board support. In order that it may slide, the sliding rod extends through two slide bearings located at a certain distance from one another.
This arrangement has the disadvantage that the bearings are heavily radially loaded in a direction which is always the same, namely the direction of the lateral reaction force which appears between the connecting rod and the sliding rod because of the angle formed between them, taking account of the angular stroke performed by the connecting rod about its axis of articulation with the sliding rod. In particular, it is the bearing closest to the articulation which is the most heavily loaded, typically by five to ten times more than the other one. These bearings are subject to their maximum load, with a jamming tendency which becomes greater as the inclination of the connection rod becomes greater, when the connecting rod pushes the sliding rod in order to make the needles penetrate into the fibrous products. Furthermore, in certain cases, the tension forces in the non-woven product are transmitted to the needles when the latter are engaged into the product. These forces on the needles can also induce lateral forces on the bearings by the intermediary of the needle board support. The result of this is that the bearings wear by becoming oval, which introduces a very harmful play in the guidance of the needle board. The replacement of these bearings requires a relatively long dismantling whilst the machine is immobilized.
The purpose of the present invention is therefore to propose a needling machine in which the problem of wear in the slide bearings is considerably lessened.